The researchers note in the article that many parts of this study are similar to previous studies done on this topic. Because of this, the assumptions made by the researchers should have been pretty much expected. Three of the four tested hypotheses turned out to be supported. Another was partially supported. The research questions were appropriate and the researchers did a good job of ensuring confidentiality. However, the survey questions themselves were not very original in that (as mentioned earlier) most of them were based on similar research. The four hypotheses or assumptions seemed like they were common sense and did not really need to be tested. Another way to explore the research question might be to conduct a quantitative study as opposed to a qualitative one. The researchers themselves admit that this study used perceptual data. That is, it was conducted based on what the participants perceived and everyone could have a different perception of the issue. A quantitatively-based test might be difficult to perform because the questions and other aspects would need to be altered or changed completely. but, this would be for the researchers to figure out.

The study results did help to answer the question, but the study seems a bit useless since the four assumptions were common sense for most. Most people know or are aware that in a work environment, a manager's...

If a subordinate feels his job is at stake if he speaks his mind to an uncooperative manager, then chances are he will not do so unless he does not care if he loses his job. Also, it stands to reason that if a manager is receptive to new ideas from his employees that those high performing employees will speak up more than low performing employees (especially if ideas from the high performers serve to advance their careers). Those performing at the lower end of the scale probably don't care enough to contribute any ideas at all.
Instead of conducting studies on assumptions which are already obvious, the researchers could have done research on managers and their perceptions of how open they are to employee suggestions. Questions could be formulated to gauge whether or not the manager is in fact open and creates an environment that is conducive to employee input. This might cut down on some of the limitations of the study because the subordinates may not answer questions truthfully about their managers no matter how much confidentiality is ensured.

References

Detert, J and Burris, E 2007, 'Leadership behavior and employee voice: Is the door really open?' Academy of Management Journal, vol. 50, no. 4, pp. 869-884.